Conductive metal lines and contacts are two of the many components typically fabricated in semiconductor processing of integrated circuitry. One example process of doing so, and problems associated therewith, is described with reference to FIG. 1. There illustrated is a semiconductor wafer fragment 10 comprised of a bulk monocrystalline silicon substrate 12. In the context of this document, the term "semiconductor substrate" or "semiconductive substrate" is defined to mean any construction comprising semiconductive material, including, but not limited to, bulk semiconductive materials such as a semiconductive wafer (either alone or in assemblies comprising other materials thereon), and semiconductive material layers (either alone or in assemblies comprising other materials). The term "substrate" refers to any supporting structure, including, but not limited to, the semiconductive substrates described above. An exemplary insulating layer 14 is formed over substrate 12. A titanium layer 16 is formed over layer 14. An example thickness for layer 16 is 400 Angstroms. An aluminum or aluminum alloy layer 18 is formed over layer 16. An example thickness is 6000 Angstroms.
Metal layers 16 and 18 in one aspect of the prior art can be conventionally deposited using physical vapor deposition semiconductor processing tools, such as the Applied Materials Endura 5500.TM. physical vapor deposition tool. Such a tool comprises multiple processing chambers within which various processing, such as pre-clean, deposition and cooling, are conducted. For example, titanium layer 16 could be deposited in a processing chamber of the tool having a titanium sputtering target received therein. Layer 18 would typically likewise be deposited in another chamber having an aluminum or an aluminum alloy sputtering target received therein. Layer 18 might also be deposited in one or multiple depositions in the same or different aluminum deposition chambers. Typically, a lattermost of such depositions, where multiple depositions are conducted, includes a high temperature sputter deposition at a temperature of, for example, 450.degree. C.
After the aluminum deposition, the wafer is typically moved to another chamber for deposition of a titanium nitride comprising layer 20. An example thickness for layer 20 is from about 150 Angstroms to about 250 Angstroms. Layer 20 is typically provided to function as an antireflective coating layer which facilitates subsequent photolithographic processing. However, it has been discovered that defects in the form of bright, circular areas or formations 22 have been forming atop layer 20 when viewed by a scanning electron microscope. These defect areas 22 have been determined to be one or combination of aluminum or aluminum oxide apparently resulting from migration of aluminum from layer 18 through cracks formed in layer 20 which exist at least during its deposition. Formation of these defect regions 22 is undesirable. It has been surmised the aluminum migrates through cracks in layer 20.
A prior art solution to the existing problem has been to position the wafer into a dedicated cooling chamber within the processing tool prior to conducting the titanium nitride deposition in a different chamber. However, the cooling takes a considerable amount of time, and effectively lengthens the amount of time it ultimately takes to process a batch of wafers utilizing the processing tool.
Accordingly, it would desirable to develop alternate methods of eliminating or at least reducing formation of defect regions 22, preferably without appreciably significantly increasing the overall processing time for a batch of wafers.